Ghostscript in Linux: CMYK PDF to CMYK EPS

Question

I have a couple of sRGB PDF figures which I'm trying to convert to CMYK EPS for an accepted paper. Since I saw no posts explaining the entire procedure in one step, I decided to first do sRGB PDF -> CMYK PDF and then CMYK PDF -> CMYK EPS. This second step is where I get stuck, but I will include the entire procedure for completeness.

I illustrate my questions using the following figures, where the first one if the input. The three figures are in the zip file https://www.dropbox.com/s/7wr84bqhp3rzagg/figs.zip?dl=0

'figure.pdf', the sRGB PDF input file
'figure_cmyk.pdf', the CMYK PDF intermediate file
'figure_cmyk.eps', the final EPS file which should be CMYK but isn't.

I will use these numbers for convenience for the rest of the question. After a couple of hours I was finally able to convert sRGB PDF (1) to CMYK PDF (2) by combining answers from Converting PDF to CMYK (with identify recognizing CMYK) . The hardest part was to let 'identify' detect that the new PDF was actually CMYK. I used Chris Hecker's hacky trick to get this conversion step to work. I then call identify with the command:

identify -format '%[colorspace]' figure_1_cmyk.pdf

and it says CMYK, so far so good. The next step should be easy I thought, just convert the CMYK PDF to CMYK EPS. But this is where I really get stuck. I am using the following bash script 'pdf2eps.sh' on (2) to get (3).

#!/bin/bash

gs \
-dNOPAUSE \
-dNOCACHE \
-dBATCH \
-dNOSUBSTDEVICECOLORS \
-sDEVICE=eps2write \
-sOutputFile="${1%%.pdf}.eps" \
"$1"

Both with and without the '-dNOSUBSTDEVICECOLORS' flag the resulting .eps file (3) somehow reverts back to sRGB as detected by 'identify'. You can check so yourself using the provided figures. I really have no idea left of what I can try, but I'm also very new to ghostscript. I would be very grateful if someone with more knowledge than me could show me how to get (3) to be CMYK.

Could it be that identify is just buggy? I don't know of other ways using linux tools to check if (3) is actually CMYK. If there are easier ways to get sRGB PDF to CMYK EPS with high quality I would be interested as well of course. The command line tool 'convert' doesn't give good results to me.

sincerely, Bram

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P.S. Since requested in one of the answers, the code I use for the first step (RGB PDF -> CMYK PDF) is the following:

bash script

#!/bin/bash

gs \
-dPDFX \
-dBATCH \
-dNOPAUSE \
-dNOOUTERSAVE \
-dPDFSETTINGS=/prepress \
-dCompatibilityLevel=1.5 \
-sDEVICE=pdfwrite \
-sColorConversionStrategy=CMYK \
-sProcessColorModel=DeviceCMYK \
-dHaveTransparency=false \
-sOutputFile="${1%%.pdf}_cmyk.pdf" \
PDFX_def_fogra39_trickcmyk.ps \
"$1"

with added file 'PDFX_def_fogra39_trickcmyk.ps'

%!
% $Id$
% This is a sample prefix file for creating a PDF/X-3 document.
% Feel free to modify entries marked with "Customize".

% This assumes an ICC profile to reside in the file (ISO Coated sb.icc),
% unless the user modifies the corresponding line below.

systemdict /ProcessColorModel known {
  systemdict /ProcessColorModel get dup /DeviceGray ne exch /DeviceCMYK ne and
} {
  true
} ifelse
{ (ERROR: ProcessColorModel must be /DeviceGray or DeviceCMYK.)=
  /ProcessColorModel cvx /rangecheck signalerror
} if

% Define entries to the document Info dictionary :

% /ICCProfile (/usr/share/color/icc/ISOcoated_v2_300_eci.icc) def  % Customize or remove.

[ /GTS_PDFXVersion (PDF/X-3:2002) % Must be so (the standard requires).
  /Title (Title)                  % Customize.
  /Trapped /False                 % Must be so (Ghostscript doesn't provide other).
  /DOCINFO pdfmark

% Define an ICC profile :

currentdict /ICCProfile known {
  [/_objdef {icc_PDFX} /type /stream /OBJ pdfmark
  [{icc_PDFX} <> /PUT pdfmark
  [{icc_PDFX} ICCProfile (r) file /PUT pdfmark
} if

% Define the output intent dictionary :

[/_objdef {OutputIntent_PDFX} /type /dict /OBJ pdfmark
[{OutputIntent_PDFX} <<
  /Type /OutputIntent              % Must be so (the standard requires).
  /S /GTS_PDFX                     % Must be so (the standard requires).
  /OutputCondition (Commercial and specialty printing) % Customize
  /Info (none)                     % Customize
  /OutputConditionIdentifier (FOGRA39)      % Customize
  /RegistryName (http://www.color.org)   % Must be so (the standard requires).
  currentdict /ICCProfile known {
    /DestOutputProfile {icc_PDFX}  % Must be so (see above).
  } if
>> /PUT pdfmark
[{Catalog} <> /PUT pdfmark

[/_objdef {OutputIntent_PDFX} /type /dict /OBJ pdfmark
[{OutputIntent_PDFX} <<
  /ColorSpace /DeviceCMYK          % convince ImageMagick's identify that it's CMYK
  /Type /OutputIntent              % Must be so (the standard requires).
  /S /GTS_PDFX                     % Must be so (the standard requires).
  /OutputCondition (Commercial and specialty printing) % Customize
  /Info (none)                     % Customize
  /OutputConditionIdentifier (CGATS TR 003)      % Customize
  /RegistryName (http://www.color.org)   % Must be so (the standard requires).
  currentdict /ICCProfile known {
    /DestOutputProfile {icc_PDFX}  % Must be so (see above).
  } if
>> /PUT pdfmark
[{Catalog} <> /PUT pdfmark

Ghostscript in Linux: CMYK PDF to CMYK EPS

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Answers (1)

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